Scientists have developed a new computer security system that lets you log in with a heart scan - using the dimensions of the organ as a unique identifier.
The system uses low-level Doppler radar to measure your heart, and then continually monitors your heart to make sure no one else has stepped in to run your computer.
The system, developed by researchers at University at Buffalo (UB) in the US, is a safe and potentially more effective alternative to passwords and other biometric identifiers.
It may eventually be used for smartphones and at airport screening barricades, researchers said.
"We would like to use it for every computer because everyone needs privacy," said Wenyao Xu, assistant professor at UB.
The signal strength of the system's radar is much less than Wi-Fi, and therefore does not pose any health threat, Xu said.
"We are living in a Wi-Fi surrounding environment every day, and the new system is as safe as those Wi-Fi devices. The reader is about five milliwatts, less than one per cent of the radiation from our smartphones," he said.
The system needs about eight seconds to scan a heart the first time, and thereafter the monitor can continuously recognise that heart.
The system, which was three years in the making, uses the geometry of the heart, its shape and size, and how it moves to make an identification.
"No two people with identical hearts have ever been found," Xu said.
People's hearts do not change shape unless they suffer from serious heart disease, he said.
Heart-based biometrics systems have been used for almost a decade, primarily with electrodes measuring electrocardiogram signals.
However, no one has done a non-contact remote device to characterise our hearts' geometry traits for identification, he said.
The new system has several advantages over current biometric tools, like fingerprints and retinal scans, Xu said.
It is a passive, non-contact device, so users are not bothered with authenticating themselves whenever they log-in.
It also monitors users constantly. This means the computer will not operate if a different person is in front of it. Therefore, people do not have to remember to log-off when away from their computers.
Xu plans to miniaturise the system and have it installed on the corners of computer keyboards. The system could also be used for user identification on cell phones.
For airport identification, a device could monitor a person up to 30 metres away.